Engineering an Interface Layer Enriching Oxygen with Nitrogen–Carbon Matrix to Enhance PtCo/C for Oxygen Reduction Reaction

A catalyst of the oxygen reduction reaction (ORR) containing as few precious metals as possible is one of the key factors for the large-scale application of fuel cells, and researchers continue to explore special catalyst structures and mechanisms to meet this requirement. We report here a catalyst named NCM⊂PtCo/C with its catalytic PtCo particles surrounded by a nitrogen–carbon matrix (NCM) as the external interface capable of enriching oxygen. The PtCo nanoparticles are confined by the NCM to a size as small as ∼2.39 nm, even after thermal treatment at high temperatures. As the reactant–catalyst interface, the electron-rich NCM layer can modulate active centers in multiple aspects, including channels for electrons and protons. Meanwhile, the NCM interface layer strongly adsorbs and holds large amounts of oxygen, causing the equivalent oxygen partial pressure in the vicinity of PtCo centers to measure ∼5 times higher than that around flowing gas, oxygen, or air. As a result, the catalyst shows a 1.5 or 2.4 times higher promotion of ORR activity compared with PtCo/C on the basis of the mass or area of Pt, respectively. The membrane electrode assembly employing the NCM⊂PtCo/C cathode catalyst achieves a peak power density of 1.6 W cm –2 at an ultralow Pt loading of 0.06 mg Pt cm –2, significantly outperforming PtCo/C. The role of the interface with oxygen enrichment in boosting the MEA performance is verified by direct quantitative evidence. Moreover, the NCM interface imparts exceptional resistance to methanol poisoning to the catalyst. We think the catalyst is highly useful for fuel cells, and the work also opens up an effective approach of developing catalysts that are practically applicable for other processes.